The present invention relates to an image processing system, a projector, a program, an information storage medium, and an image processing method capable of correcting image distortion.
An image may be distorted due to the relative angle formed by the optical axis of projection light from an image projection device such as a projector and a projection target such as a screen, whereby keystone distortion may occur in the vertical direction or horizontal direction.
Therefore, the image display device must display an image while eliminating distortion of the image.
A conventional projector with an image distortion correction function corrects image distortion only in the vertical direction using a built-in angle sensor, and cannot correct image distortion in the horizontal direction.
In the case of correcting image distortion in the horizontal direction, a user points at the four corners of the screen using a mouse or the like, and the projector semi-automatically corrects image distortion based on the point information. However, it is troublesome for the user to point at the four corners of the screen using a mouse or the like.
In order to solve such a problem, Japanese Patent Application Laid-open No. 2000-241874 has disclosed an automatic screen position adjustment device for a projector which detects the position of the screen in an image sensed by using a monitor camera based on an image signal input from the monitor camera, and adjusts keystone distortion of the projected image based on the detected screen position data.
In the method disclosed in Japanese Patent Application Laid-open No. 2000-241874, keystone distortion is adjusted by comparing the lengths of opposite sides of the screen in the sensed monitor screen as described in the specification of Japanese Patent Application Laid-open No. 2000-241874.
However, in the case where the height/width ratio (aspect ratio) of the projection target such as the screen is unknown, the projector cannot appropriately determine image distortion merely by comparing the lengths of opposite sides of the screen.
Japanese Patent application Laid-open No. 2002-247614 has disclosed a projector which detects the external shape of a screen by using a sensing section, and corrects an image so that the image has an external shape the same as the detected external shape.
However, if the projector changes the shape of the image into the external shape of the screen as disclosed in Japanese Patent application Laid-open No. 2002-247614, the image after changing has an external shape differing from the external shape of the original image. In this case, since an observer is given an impression differing from the original image, it is not preferable to employ such a processing method.
Moreover, it is preferable that a projected image be displayed at a desired height/width ratio even if the height/width ratio of the projection target is used as a reference.